Engine bearing

ABSTRACT

A journal bearing has a lining of bearing metal applied to a steel backing. The surface of the lining is laser peen hardened to locally increase the hardness and the seizure resistance of the lining. The underlying core of the lining is unaffected and maintains good conformability of the lining. The overall lining thus possesses both good seizure resistance and conformability.

BACKGROUND OF THE INVENTION

1. Technical Field

This invention relates generally to journal or engine bearings forinternal combustion engines, and more particularly to the constructionof linings for journal bearings.

2. Related Art

Sliding-type journal or engine bearings are typically used in internalcombustion engine applications for journaling a shaft of the engine.Typical engine bearings have an arcuate steel backing onto which one ormore layers of relatively softer bearing metal is applied.

The steel backing provides structural rigidity to the bearing whereasthe applied bearing layer or layers provide a low friction slidingsurface that must exhibit a combination of seemingly incompatibleproperties of acceptable wear and fatigue resistance, and acceptableconformability and seizure-resistance. The first two properties call fora hard, strong bearing material, whereas conformability and seizureresistance call for a softer material of lesser strength. It isgenerally accepted that no one material can satisfy all criteria, sincea material cannot be both hard and soft. Accordingly, the currentpractice is to select a material, or multiple layer materials, thatcompromise between the competing properties. However, the demand forever-increasing performance of engine bearings continues to challengeability to provide a suitable “compromise” bearing material at anacceptable cost. Modern bearings and those of the future requireever-increasing wear and fatigue resistance properties withoutsacrificing the conformability of the bearings. As the demands of thesecompeting properties get driven further apart, a suitable compromisematerial(s) is becoming more difficult to attain.

It is an object of the present invention to overcome or greatly minimizethe foregoing limitations of prior engine bearings.

SUMMARY OF THE INVENTION

An engine bearing for an internal combustion engine has a lining with ahardened surface layer providing the journal bearing with an extendedlife in use. The bearing has an arcuate backing comprised of a firstmaterial having an outer surface and an inner surface. A liningcomprised of a second material different from the first material isfixed to the inner surface of the backing. According to the invention,the lining is laser peened (also known as “laser shock hardened”) toimpart compressive residual stresses in a surface region to produce ahardened skin with enhanced fatigue and wear resistance while anunderlying core of the lining is unaffected and possesses goodconformability and seizure resistance.

One advantage of the present invention is that a journal type bearing isprovided having an extended life in use.

Another advantage of the invention is that a greater variety of bearingmetals are available that can satisfy the competing properties offatigue resistance and conformability.

THE DRAWINGS

These and other features and advantages of the present invention willbecome more readily appreciated when considered in connection with thefollowing detailed description and appended drawings, wherein:

FIG. 1 is a perspective view of a presently preferred embodiment of ajournal bearing embodying the present invention;

FIG. 2 is a cross sectional view taken along the line 2—2 of FIG. 1; and

FIG. 3 is an enlarged and magnified plan view of one-half of the journalbearing of FIG. 1.

DETAILED DESCRIPTION

A presently preferred embodiment of a journal bearing constructedaccording to the present invention is shown generally at 10 in FIGS.1-3. The journal bearing 10 has a backing plate 12 and a lining 14. Thebacking plate 12 provides rigidity to the journal bearing 10.

The backing plate 12 is formed of a first material, preferably steel,and has an outer arcuate convex surface 18 and an inner arcuate concavesurface 20.

The lining 14 is formed from a second lining material different thanthat of the backing plate material. Preferably, the lining materialcomprises either an aluminum-based or copper-based alloy material. Thelining 14 has a first side 22 and a second side 24. The first side 22 ofthe lining 14 is fixed to the inner surface 20 of the backing plate 12.The second side 24 of the lining 14 defines an inner arcuate bearingsurface 16 that is spaced radially inwardly from the backing plate 12.

To improve the strength characteristics of the bearing surface 16, thesecond side 24 of the lining 14 is treated by laser peening or lasershock peening, which is known per se for the treatment of materialsgenerally, but not known in connection with engine bearings to increasefatigue resistance while preserving conformability and seizureresistance of a bearing lining material. The laser peened treatmentinduces residual compressive stresses which serve to locally hardenouter layer region 26 of the lining 14. The hardened layer 26 improvesthe fatigue resistance of the bearing surface 16 by inhibiting crackinitiation and propagation within and through the bearing surface 16. Asa result, the service life of the journal bearing 10 is extended.

The laser surface peening process subjects the second side 24 of thelining 14 to a laser pulse with a power density of approximately 1gigawatt/cm² with an interaction time of approximately 1 microsecond.

The lining 14 has a non-laser peened layer or core 28 between thehardened layer 26 and the backing 12. Typically, upon laser peening thesecond side 24, the hardened layer 26 takes on a hardness value ranginganywhere between 0-5 points on the Vickers scale greater than thehardness of the core 28, though this range can be increased depending onthe laser surface peening parameters. Though the bearing surface 16 isharder than the core layer 28 of the lining 14, the bearing surface 16and core 28 retain a combined desirable level of conformability, withthe core 28 exhibiting greater conformability than that of the hardenedlayer 26.

The hardened layer 26 preferably extends to a depth of about 20 to 50micrometers below the surface 16. As such, the conformability of thecore 28, and thus the overall lining is largely unaffected, as theconformability has been formed to be influenced primarily within a depthof ¼-½ mm below the bearing surface 16. Conformability of the journalbearing is particularly beneficial in applications that are prone tomisalignment of the shaft relative to the journal bearing, thus causingan effect commonly referred to as “edge loading.” In addition, anyimperfections in machining of the shaft, such as a crank shaft in aninternal combustion engine, can reduce the useful life of the journalbearing 10 if adequate conformability is not provided in the lining 14of the journal bearing 10.

In journal bearing applications it is common for contaminants or debristo come in contact with the journal bearing 10. Thus, it is desirable toprovide journal bearings that can operate in the presences ofcontaminants or debris without negatively impacting the useful life ofthe journal bearings. The journal bearing 10, having a bearing surface16 and a hardened layer 26 does not impair the embedability propertiesof the journal bearing 10 to retain contamination or debris within thebearing surface 16.

According to a further aspect of the invention, the laser peening may beadvantageously controlled to develop a particular textured surface 30 ofthe hardened layer 26. For example, as best shown in FIG. 3, the surfacetexturing 30 provides for circumferentially extending grooves,represented here as a plurality of generally parallel grooves, promotingthe retention of lubrication and enhanced hydrodynamic action on thebearing surface 16 of the journal bearing 10. The surface texturing 30is formed during the laser surface peening process by directing theshock waves to the desired location on the second side 24 of the lining14. While a grooved texture is illustrated by way of example, theinvention contemplates other textures, for example, grooves in otherdirections, such as axial grooves.

Obviously, many modifications and variations of the present inventionare possible in light of the above teachings. It is, therefore, to beunderstood that within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described. The inventionis defined by the claims.

1. An engine bearing for an internal combustion engine, comprising: anarcuate metal backing plate; a lining of bearing metal different thanthat of the backing plate applied to said backing plate and presentingan inner arcuate surface; and said inner arcuate surface of said liningbeing peened to induce compressive residual stresses in said innerarcuate surface to define a locally hardened surface layer of saidlining backed by a core of said lining, wherein said hardened surfacelayer has a hardness and fatigue strength exceeding that of said core,and said core is relatively more conformable than that of said hardenedsurface layer and wherein said hardened surface layer extends about 20to 50 micrometers below said inner arcuate surface.
 2. The enginebearing of claim 1 wherein said backing plate is fabricated of steel. 3.The engine bearing of claim 1 wherein said bearing metal comprises analuminum-based alloy.
 4. The engine bearing of claim 1, wherein saidcore extends from said hardened layer to said backing plate.
 5. Theengine bearing of claim 1 further comprising a textured surface on saidhardened surface layer.
 6. The engine bearing of claim 1 wherein saidtextured surface comprises circumferential grooves.
 7. The enginebearing of claim 1 wherein said core has a hardness less than both saidarcuate metal backing plate and said hardened surface layer.
 8. Anengine bearing for an internal combustion engine, comprising: an arcuatemetal backing plate; a lining of bearing metal different than that ofthe backing plate applied to said backing plate and presenting an innerarcuate surface; and said inner arcuate surface of said lining beingpeened to induce compressive residual stresses in said inner arcuatesurface to define a locally hardened surface layer of said lining backedby a core of said lining, wherein said hardened surface layer has ahardness and fatigue strength exceeding that of said core, and said coreis relatively more conformable than that of said hardened surface layerand wherein said hardened surface layer has a hardness about 0 to 5points greater on a Vickers scale than said core of said lining.
 9. Theengine bearing of claim 8 wherein said backing plate is fabricated ofsteel.
 10. The engine bearing of claim 8 wherein said bearing metalcomprises an aluminum-based alloy.
 11. The engine bearing of claim 8wherein said core extends from said hardened layer to said backingplate.
 12. The engine bearing of claim 8 further comprising a texturedsurface on said hardened surface layer.
 13. The engine bearing of claim8 wherein said textured surface comprises circumferential grooves. 14.An engine bearing for an internal combustion engine, comprising: anarcuate metal backing plate; a lining of bearing metal different thanthat of the backing plate applied to said backing plate and presentingan inner arcuate surface; and said inner arcuate surface of said liningbeing laser peened to induce compressive residual stresses in said innerarcuate surface to define a locally hardened surface layer of saidlining backed by a core of said lining, wherein said hardened surfacelayer has a hardness and fatigue strength exceeding that of said core,and said core is relatively more conformable than that of said hardenedsurface layer, and wherein said laser peened surface defines a patternof circumferential grooves on said inner arcuate surface of said lining.